Five hundred and forty-two cases of pyoderma were investigated to study bacterial aetiology and their antibiotic susceptibility patterns. Of these 65.87% cases were of primary pyoderma and the rest were of secondary pyoderma. Maximum cases were of impetigo (38.78%) followed by folliculitis (12.92%), furunculosis (2.95%), ecthyma (3.5%), carbuncle (1.5%) and sycosis barbae (0.4%). Secondary pyoderma constituted infected trophic ulcer (18.82%), infected pemphigus (7.2%), infected contact dermatitis (6.27%), and infected scabies (1.8%). Single organism was isolated from 46.9% cases and more than one type of organisms in 65.46% of cases. No organism was isolated in 5% of cases. Staphylococcus (67.34%) was the predominant species isolated followed by beta-haemolytic streptococcus (21.77%). Maximum strains of Staph. aureus were susceptible to amikacin (75%), co-trimoxazole (72%), cefotaxime (65%), chloramphenicol (62%), ciprofloxacin (61%) and clindamycin (61%). There was low susceptibility to cephaloridin (11%), gentamicin (12%) and penicillin (21%). Streptococcus betahaemolyticus was highly sensitive to most of the antibiotics and less sensitive to cefotaxime (7%), co-trimoxazole (11%) and penicillin (27%). Most of the strains were found to be resistant to one or more antibiotics.

Keywords: Pyoderma, Antibiotic susceptibility

How to cite this article:Ghadage D P, Sali Y A. Bacteriological study of pyoderma with special reference to antibiotic susceptibility to newer antibiotics. Indian J Dermatol Venereol Leprol 1999;65:177-81

Pyoderma is quite common in India and constitutes a major portion of patients in Dermatology clinics. Many cases do not respond to some antibiotics which were previously very effective for such cases. Perhaps indiscriminate use of topical and systemic antibiotics has contributed to this situation.[3][4][5][6][7][8][9][10][11][12][13] Increasing resistance to antibiotics seen in microorganisms poses a big problem to the clinicians. So for successful treatment of cases of pyoderma a detailed knowledge about the causative microorganisms should be available. Hence keeping this view in mind the present study was designed on pyodermas to find out causative organisms and their latest antibiotic susceptibility patterns.

Materials and Methods

We studied 542 cases of pyoderma of various age groups and of either sex attending the Skin O.P.D. of the Sassoon General Hospitals, Pune. The samples were collected before the antibiotic therapy was started. Specimens of pus were collected aseptically with the help of two sterile swabs. The swabs were transported immediately to the laboratory. Of the two swabs collected one was used for Gram stain and microscopic examination and the other for culture. Second swab was inoculated on to the following media.

Blood agar

MacConkey's agar

Crystal violet blood agar (1:500000 of crystal violet in blood)

MacConkey's agar plate was used for Gram negative bacilli while crystal violet blood agar was used for the growth of streptococci. Blood agar and crystal violet blood agar were incubated in 5-10% CO2. Inoculated media were incubated aerobically at 37° C for 24 hrs. The organisms grown were identified by standard conventional method.[1] Antibiotic susceptibility testing of isolated organisms was performed on Muller Hinton agar and blood agar by modified Kirby Bauer disc diffusion method.[2]

Results and Observations

Males were affected more than females. It is observed that more patients belonged to adult age group than paediatric age group [Table - 1]

Primary pyoderma constituted 69.5% of cases and rest were of secondary pyoderma. There were 39% cases of impetigo, 13% of folliculitis, 6% of cellulitis, 3.5% of ecthyma, 3% of furunculosis, 1.5% of carbuncle and 0.4% of sycosis barbae. [Table - 2]

A single infecting organism was isolated from 46.9% cases and more than one type of organism from 65.46% cases. No organism was isolated from 5% cases. Staphylococcus was isolated alone from 67.35% cases, out of which coagulase negative staphylococci was isolated from 23.6% cases. Coagulase positive staphylococci (43.7%) was the predominant species followed by beta haemolytic streptococci (21.7%). [Table - 3]

Discussion

Five hundred and forty-two cases of pyoderma were investigated for bacterial aetiology. Impetigo formed the largest group followed by folliculitis, furunculosis, ecthyma, carbuncle and sycosis barbae in descending order of frequency. Similar high incidence of impetigo was reported by others.[3][4][5][6] It is observed that more patients belonged to adult age group. Males were affected more than females. Similar findings were reported by others.[6][][9]

In the bacteriological analysis we observed that staphylococcus (67.34%) was the predominant species isolated.[4][5] Beta haemolytic streptococcus was the next common aetiological agent. [5, 6] Staphylococci were isolated singly or in association with other organisms.

Among the staphylococci strains isolated 43.72% were coagulase positive and 23.61% were coagulase negative. High incidence of coagulase positive staphylococci in pyoderma was reported by several workers.[4-6, 8] Coagulase negative strains were also reported to be aetiologic agents[5][8]. Staph aureus and beta-haemolytic streptococci are considered to be main aetiological agents. These have been isolated in different percentages in India and abroad.[9-11]

Number of other organisms were isolated (25.27%) from cases of pyoderma in this study which were non-haemolytic streptococci, pseudomonas spp, proteus spp., Citrobacter spp., klebsiella spp., Esch. coli, acinetobacter spp [5, 6].

Percentage of antibiotic susceptibility patterns of various isolates are shown in [Table - 4].

Most of the strains were found to be resistant to one or more antibiotics. [5, 7, 8] Penicillin resistance of coagulase positive staphylococci was reported by several workers.[9-13] Most of the organisms were sensitive to newer antibiotics. Multiple drug resistance was observed to currently used antibiotics.[11][12][13]

In conclusion, this study gives an indication of the present state of pyodermas. Multidrug resistance has become a clinical challenge. Most of the strains were found to be resistant to one or more antibiotics. It is probably due to indiscriminate use of antibiotics which must be avoided. Newer antibiotics must always be kept in reserve for use only against strains resistant to common antibiotics. Proper antibiotic therapy can be given avoiding unnecessary medication with drugs known to be useless. For the selection of proper antibiotics in vitro testing is essential.